The list of approved microbicidal agents has decreased due to their human toxicity and their detrimental effect on water supplies and the environment. Improving analytical capabilities to detect parts-per-billion levels in food, water and in the environment have raised important safety concerns about the application and misapplication of these chemicals. These issues have resulted in the banning of some antimicrobials, for example hexachlorophene; the retesting of others for animal toxicity, such as, the quaternary ammonium compounds; and, the increasing scrutiny of microbicidal species such as chlorine or hypochlorites which may form toxic halocarbons in effluent waters.
There has been a long felt need for antimicrobial agents which have a high degree of antimicrobial efficacy, and which are preferably safely ingestible by humans while posing no environmental incompatibility. Those antimicrobial agents which are lethal to microorganisms, however, are also toxic in varying degrees to humans and animals in that both higher and lower forms of life share at least some metabolic pathways. Competitive inhibition, non-competitive inhibition, protein coagulation, oxidative and reductive action, blockage of enzyme systems are thought to be some of the mechanisms involved in the destruction of microorganisms.
Differentiation of antimicrobial "-cidal" or "-static" activity, the definitions which describe the degree of efficacy, and the official laboratory protocols for measuring this efficacy are important considerations for understanding the relevance of antimicrobial agents and compositions. Antimicrobial compositions may effect two kinds of microbial cell damage. The first is a truly lethal, irreversible action resulting in complete microbial cell destruction or incapacitation. The second type of cell damage is reversible, such that if the organism is rendered free of the agent, it can again multiply. The former is termed bactericidal and the latter, bacteriostatic. A sanitizer and a disinfectant are, by definition, agents which provide bactericidal activity. In contrast, a preservative is generally described as inhibitory or bacteriostatic.
A sanitizer is an agent that reduces the number of bacterial contaminants to safe levels as judged by public health requirements. Practically, a sanitizer must result in 99.999% reduction (5 log order reduction) for given organisms as defined by Germicidal and Detergent Sanitizing Action of Disinfectants, Official Methods of Analysis of the Association of Official Analytical Chemists, paragraph 960.09 and applicable sections, 15th Edition, 1990 (EPA Guideline 91-2). In common practice, substances that are applied to food contact surfaces for antimicrobial purposes must meet this requirement.
A disinfectant is an agent that kills all vegetative cells including most recognized pathogenic microorganisms. As such, it must pass a more stringent bactericidal test; the A.O.A.C. Use Dilution Methods, Official Methods of Analysis of the Association of Official Analytical Chemists, paragraph 955.14 and applicable sections, 15th Edition, 1990 (EPA Guideline 91-2).
In contrast, a preservative is described as any agent that extends the storage life of food and non-food products by retarding or preventing deterioration of flavor, odor, color, texture, appearance, nutritive value, or safety. One method used for evaluating such materials is designated Minimum Inhibitory Method Concentration. Another procedure is entitled Zone of Inhibition. Preservatives, by definition, are therefore inhibitory substances added to food to prolong or enhance shelf-life. The principal differences between a preservative and a sanitizer are two-fold; 1) mode of action, a preservative prevents growth rather than killing microorganisms; and, 2) exposure time, a preservative has days to months. In contrast, a sanitizer must provide 99.999% kill (5 log order) within 30 seconds at nominal 20.degree. C.
Ideally, a sanitizing agent or compound will possess several important properties in addition to its microbicidal efficacy. The sanitizer should be no-rinse after application, and have residual antimicrobial activity. Residual activity implies a film of sanitizing material which will continue to have antimicrobial effect if the treated surface is contaminated by microorganisms during a storage or lag period. The sanitizer should be odor free to prevent transfer of undesirable odors onto foodstuffs. The sanitizer should be composed of direct food additive materials which will not affect food if contamination occurs, nor affect humans should incidental ingestion result. In addition, the sanitizer should be composed of naturally occurring or innocuous ingredients, which are chemically compatible with the environment and cause no concern for toxic residues in downstream water.
Previously, certain compositions have been recognized as effective in maintaining the condition of food products. For example, U.S. Pat. No. 4,404,040 to Wang discloses the sanitizing properties of short chain fatty acids formulated with an ionic hydrotrope-solubilizer and compatible acids. However, Wang does not focus on the antimicrobial efficacy of octanoic acid specifically or the efficacy of this compound when used with certain adjuvants. Wang also does not focus on food additive compositions. U.S Pat. No. 4,647,458 to Ueno et al, discloses bactericidal compositions comprising a large concentration of ethyl alcohol, an organic acid, and an inorganic acid. However, Ueno et al use a large concentration of ethanol and do not discuss the activity of C.sub.8 acids.
Moreover, U.S. Pat. No. 3,915,633 to Ramachandran, discloses a prewash composition for treating fabrics which includes an organic acid such as citric acid and either a nonionic or an anionic surfactant. U.S. Pat. No. 3,867,300 to Karabinos, discloses bactericidal compositions presumably for controlling the spread of nosocomial infections in hospitals consisting of an aliphatic monocarboxylic acids, and nonionic surfactants. U.K. Patent Application GB 2,103,089A to Kimberly Clark discloses the use of carboxylic acids as virucides. U.S. Pat. No. 4,715,980 to Lopes et al, discloses an antimicrobial concentrate composition containing a dicarboxylic acid, a solubilizer, an acid, and a diluent. U.S. Pat. No. 3,650,965 to Cantor et al, discloses clean-in-place detergent solutions for treating milk and food processing equipment based on two different nonionic surfactants.
U.S. Pat. No. 4,002,775 to Kabara discloses the use of mono-esters of twelve carbon aliphatic fatty acids and polyols. European Patent Application No. 87303488 to Kabara discloses antimicrobial preservative compositions of glyceryl mono esters, preferably monolaurin and fatty acids. However, similar to Wang and Ueno et al, the disclosure in these publications is not specific to C.sub.8 acids and further does not discuss the antimicrobial activity of these acids in conjunction with their use with certain adjuvants.
Currently, products used for sanitizing operations include strong oxidizing agents such as peracetic acid, iodophors, sodium hypochlorite and related n-chloro compounds such as chloro isocyanurates, quaternary ammonium compounds, acid compositions containing dodecylbenzenesulfonic acid or carboxylic acid and the like. While these are no rinse sanitizers, they are not ideal for one reason or another.
Peracetic acid, iodophors and chlorine based sanitizers are either decomposed or lost by evaporation when a film of sanitizer is left on food contact surface and allowed to dry. Thus no residual activity remains on the intended surface. Residual activity is necessary to provide continued antimicrobial effect if the surface is contaminated by microorganisms during storage.
Quaternary ammonium compounds (QAC) have an excellent residual quality as they are stable and increase in concentration as the solvent (water) evaporates. Unfortunately, for many uses, this residue may carry into a food product. In fact, even a trace of QAC in milk inhibits the starter culture which produces lactic acid and flavor resulting in the curdling of milk protein. Acid based sanitizers often contain foam control agents or surfactant couplers which are not food additive. Moreover, carboxylic acid based sanitizers often have undesirable organoleptic properties exemplified by a "goat-like" odor. The longer chain fatty acids have limited solubilities in water and require thorough rinsing with potable water before contact of the sanitized surface with food stuff to avoid imparting off-flavor to the food.
While all these compositions are excellent sanitizers, many of their ingredients are not food additive. Consequently, these current, commercially successful products have not been designed for user safety, misapplication or environmental compatibility. Thus a sanitizing agent which specifically addresses these issues would possess utility and uniqueness not found in heretofore described sanitizers.